On the asynchronous side, we've developed a few fun conversation starters, like a daily "the more you know" Slack message and a weekly "icebreaker" (also over Slack). The conversations that come out of these simple prompts are both insightful and entertaining.
Think of ways to sprinkle fun throughout each medium of asynchronous communication that your team uses (docs, emails, Slack, etc.). Remember, it's important to not over-prescribe fun. Some of our favorite traditions have spontaneously emerged as we encourage and support a culture of fun. Working remotely can sometimes feel lonely, and asynchronous fun and laughter can be one of the best cures.